Bottle caps seal well and work just fine. The only problem is how other may perceive your wine.

Screw 'em - If they don't like the bottles the free booze comes in, they don't have to have any

Seriously, I was thinking of wine bottles for stuff I know we'll get through in a couple of days (grape, Apple) and for bottles I know will be gifted away, and 250ml Bottles (i.e. 2 regular or one large glass) for anything more unusual.